OpenCV in Android Studio

Question

I want to use OpenCV library in my app with Android Studio  I followed instructions found here but I get error      Configuration with name  default  not found   What can be wrong   I use Android Studio 1 0 with gradle 2 2 1

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Anybody facing problemn while creating jniLibs cpp is shown   just add ndk

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This worked for me and was as easy as adding a gradle dependancy   https   bintray com seesaa maven opencv   https   github com seesaa opencv-android  The one caveat being that I had to use a hardware debugging device as arm emulators were running too slow for me  as AVD Manager says they will   and  as described at the repo README  this version does not include x86 or x86 64 support    It seems to build and the suggested test   static       OpenCVLoader initDebug        spits out a bunch of output that looks about right to me

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In your build gradle repositories     jcenter      implementation  com quickbirdstudios opencv 4 1 0   More information

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Download  Get the latest pre-built OpenCV for Android release from https   github com opencv opencv releases and unpack it  for example  opencv-4 4 0-android-sdk zip   Create an empty Android Studio project Open Android Studio  Start a new project     Keep default target settings  Use  quot Empty Activity quot  template  Name activity as MainActivity with a corresponding layout activity main  Plug in your device and run the project  It should be installed and launched successfully before we ll go next   Add OpenCV dependency  Go to File- gt New- gt Import module and provide a path to unpacked OpenCV package sdk java  The name of module detects automatically  Disable all features that Android Studio will suggest you on the next window    Configure your library build gradle  openCVLibrary build gradle  apply plugin   com android library   android       compileSdkVersion 28     buildToolsVersion  quot 28 0 3 quot       buildTypes           release               minifyEnabled false             proguardFiles getDefaultProguardFile  proguard-android txt     proguard-rules txt                     Implement the library to the project  application build gradle   implementation project   openCVLibrary330

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Integrating OpenCV v3 1 0 into Android Studio v1 4 1  instructions with additional detail and this-is-what-you-should-get type screenshots   Most of the credit goes to Kiran  Kool  1   and SteveLiles over at opencv org for their explanations   I m adding this answer because I believe that Android Studio s interface is now stable enough to work with on this type of integration stuff   Also I have to write these instructions anyway for our project   Experienced A S  developers will find some of this pedantic   This answer is targeted at people with limited experience in Android Studio    Create a new Android Studio project using the project wizard  Menu  File New Project     Call it  cvtest1  Form factor   API 19  Android 4 4  KitKat  Blank Activity named MainActivity  You should have a cvtest1 directory where this project is stored    the title bar of Android studio shows you where cvtest1 is when you open the project   Verify that your app runs correctly   Try changing something like the  Hello World  text to confirm that the build test cycle is OK for you    I m testing with an emulator of an API 19 device   Download the OpenCV package for Android v3 1 0 and unzip it in some temporary directory somewhere    Make sure it is the package specifically for Android and not just the OpenCV for Java package    I ll call this directory  unzip-dir   Below unzip-dir you should have a sdk native libs directory with subdirectories that start with things like arm     mips    and x86      one for each type of  architecture  Android runs on  From Android Studio import OpenCV into your project as a module  Menu  File New Import Module    Source-directory    unzip-dir  sdk java Module name   Android studio automatically fills in this field with openCVLibrary310  the exact name probably doesn t matter but we ll go with this   Click on next   You get a screen with three checkboxes and questions about jars  libraries and import options   All three should be checked   Click on Finish   Android Studio starts to import the module and you are shown an import-summary txt file that has a list of what was not imported  mostly javadoc files  and other pieces of information     But you also get an error message saying failed to find target with hash string  android-14       This happens because the build gradle file in the OpenCV zip file you downloaded says to compile using android API version 14  which by default you don t have with Android Studio v1 4 1    Open the project structure dialogue  Menu  File Project Structure    Select the  app  module  click on the Dependencies tab and add  openCVLibrary310 as a Module Dependency   When you select Add Module Dependency it should appear in the list of modules you can add  It will now show up as a dependency but you will get a few more cannot-find-android-14 errors in the event log  Look in the build gradle file for your app module   There are multiple build gradle files in an Android project   The one you want is in the cvtest1 app directory and from the project view it looks like build gradle  Module  app    Note the values of these four fields    compileSDKVersion   mine says 23  buildToolsVersion  mine says 23 0 2  minSdkVersion  mine says 19  targetSdkVersion  mine says 23   Your project now has a cvtest1 OpenCVLibrary310 directory but it is not visible from the project view      Use some other tool  such as any file manager  and go to this directory   You can also switch the project view from Android to Project Files and you can find this directory as shown in this screenshot    Inside there is another build gradle file  it s highlighted in the above screenshot    Update this file with the four values from step 6    Resynch your project and then clean rebuild it    Menu  Build Clean Project   It should clean and build without errors  and you should see many references to  openCVLibrary310 in the 0 Messages screen     At this point the module should appear in the project hierarchy as openCVLibrary310  just like app    Note that in that little drop-down menu I switched back from Project View to Android View     You should also see an additional build gradle file under  Gradle Scripts  but I find the Android Studio interface a little bit glitchy and sometimes it does not do this right away   So try resynching  cleaning  even restarting Android Studio   You should see the openCVLibrary310 module with all the OpenCV functions under java like in this screenshot    Copy the  unzip-dir  sdk native libs directory  and everything under it  to your Android project  to cvtest1 OpenCVLibrary310 src main   and then rename your copy  from libs to jniLibs   You should now have a cvtest1 OpenCVLibrary310 src main jniLibs directory   Resynch your project and this directory should now appear in the project view under openCVLibrary310    Go to the onCreate method of MainActivity java and append this code   if   OpenCVLoader initDebug          Log e this getClass   getSimpleName       OpenCVLoader initDebug    not working       else       Log d this getClass   getSimpleName       OpenCVLoader initDebug    working         Then run your application   You should see lines like this in the Android Monitor    I don t know why that line with the error message is there  Now try to actually use some openCV code   In the example below I copied a  jpg file to the cache directory of the cvtest1 application on the android emulator   The code below loads this image  runs the canny edge detection algorithm and then writes the results back to a  png file in the same directory     Put this code just below the code from the previous step and alter it to match your own files directories   String inputFileName  simm 01   String inputExtension    jpg   String inputDir   getCacheDir   getAbsolutePath        use the cache directory for i o String outputDir   getCacheDir   getAbsolutePath    String outputExtension    png   String inputFilePath   inputDir   File separator   inputFileName         inputExtension    Log d  this getClass   getSimpleName     loading     inputFilePath           Mat image   Imgcodecs imread inputFilePath     Log d  this getClass   getSimpleName     width of     inputFileName          image width        if width is 0 then it did not read your image       for the canny edge detection algorithm  play with these to see different results int threshold1   70  int threshold2   100   Mat im canny   new Mat        you have to initialize output image before giving it to the Canny method Imgproc Canny image  im canny  threshold1  threshold2   String cannyFilename   outputDir   File separator   inputFileName     canny-    threshold1    -    threshold2         outputExtension  Log d  this getClass   getSimpleName     Writing     cannyFilename   Imgcodecs imwrite cannyFilename  im canny    Run your application   Your emulator should create a black and white  edge  image   You can use the Android Device Monitor  to retrieve the output or write an activity to show it    The Gotchas    If you lower your target platform below KitKat some of the OpenCV libraries will no longer function  specifically the classes related to org opencv android Camera2Renderer and other related classes   You can probably get around this by simply removing the apprpriate OpenCV  java files  If you raise your target platform to Lollipop or above my example of loading a file might not work because use of absolute file paths is frowned upon   So you might have to change the example to load a file from the gallery or somewhere else   There are numerous examples floating around

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The below steps for using Android OpenCV sdk in Android Studio   This is a simplified version of this 1  SO answer    Download latest OpenCV sdk for Android from OpenCV org  and decompress the zip file  Import OpenCV to Android Studio  From File -  New -  Import Module  choose sdk java folder in the unzipped opencv archive    Update build gradle under imported OpenCV module to update 4 fields to match your project build gradle a  compileSdkVersion b  buildToolsVersion c  minSdkVersion and d  targetSdkVersion    Add module dependency by Application -  Module Settings  and select the Dependencies tab  Click   icon at bottom  choose Module Dependency and select the imported OpenCV module    For Android Studio v1 2 2  to access to Module Settings   in the project view  right-click the dependent module -  Open Module Settings    Copy libs folder under sdk native to Android Studio under app src main    In Android Studio  rename the copied libs directory to jniLibs and we are done    Step  6  is since Android studio expects native libs in app src main jniLibs instead of older libs folder  For those new to Android OpenCV  don t miss below steps     include static  System loadLibrary  opencv java       Note  for OpenCV version 3 at this step you should instead load the library opencv java3   For step 5   if you ignore any platform libs like x86  make sure your device emulator is not on that platform    OpenCV written is in C C    Java wrappers are    Android OpenCV SDK - OpenCV org maintained Android Java wrapper  I suggest this one  OpenCV Java - OpenCV org maintained auto generated desktop Java wrapper  JavaCV - Popular Java wrapper maintained by independent developer s   Not Android specific  This library might get out of sync with OpenCV newer versions

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Android Studio 3 4   OpenCV 4 1   Download the latest OpenCV zip file from here  current newest version is 4 1 0  and unzip it in your workspace or in another folder  Create new Android Studio project normally  Click File- gt New- gt Import Module  navigate to  path to unzipped files OpenCV-android-sdk sdk java  set Module name as opencv  click Next and uncheck all options in the screen  Enable Project file view mode  default mode is Android   In the opencv build gradle file change apply plugin   com android application  to apply plugin   com android library  and replace application ID  org opencv  with  minSdkVersion 21 targetSdkVersion 28    according the values in app build gradle   Sync project with Gradle files  Add this string to the dependencies block in the app build gradle file  dependencies               implementation project path    opencv              Select again Android file view mode  Right click on app module and goto New- gt Folder- gt JNI Folder  Select change folder location and set src main jniLibs   Select again Project file view mode and copy all folders from  path to unzipped files OpenCV-android-sdk sdk native libs to app src main jniLibs  Again in Android file view mode right click on app module and choose Link C   Project with Gradle  Select Build System ndk-build and path to OpenCV mk file  path to unzipped files OpenCV-android-sdk sdk native jni OpenCV mk   path to unzipped files must not contain any spaces  or you will get error    To check OpenCV initialization add Toast message in MainActivity onCreate   method   Toast makeText MainActivity this  String valueOf OpenCVLoader initDebug     Toast LENGTH LONG  show      If initialization is successful you will see true in Toast message else you will see false

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For everyone who felt they want to run away with all the steps and screen shots on the  great   above answers  this worked for me with android studio 2 2 1   Create a new project  name it as you want and take the default  minSdkVersion 15 is fine    Download the zip file from here  https   sourceforge net projects opencvlibrary files opencv-android    I downloaded 3 2 0 version  but there may be a newer versions    Unzip the zip file  the best place is in your workspace folder  but it not really matter   Inside Android Studio  click File- gt New- gt  Import Module and navigate to  path to your unzipped file OpenCV-android-sdk sdk java and hit Ok  then accept all default dialogs   In the gradle file of your app  module  add this to the dependencies block   dependencies        compile project   openCVLibraryXYZ          rest of code       Where XYZ is the exact version you downloaded  for example in my case      dependencies           compile project   openCVLibrary320             rest of code

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